1. Field of the Invention
The present invention relates to a light-emitting device and manufacturing method thereof, and more particularly, to a flip-chip type light-emitting device having improved light extraction efficiency and heat emission efficiency, and a manufacturing method thereof.
2. Background of the Related Art
Recently, along with the development of the optics and electronics fields, the industrial demand for a transparent conducting film with high light transmittance and electrical conductivity is increasing. Such a transparent conducting film is necessarily used for a flat panel display device, a solar cell, a transparent touch panel and the like.
Semiconductor light-emitting device which converts electrical signals into optical signals using the characteristics of semiconductors, i.e., light-emitting devices such as light-emitting diodes (LEDs) or laser diode (LDs) are widely researched and put into practice use in a variety of application fields such as illumination, optical communication, multiplex communication and the like. Such semiconductor light-emitting devices are widely used as light sources of means for transmitting data or writing/reading data in communication devices or devices such as disk players.
FIG. 1 is a cross-sectional view illustrating one example of a conventional nitride-based semiconductor light-emitting device according to the prior art.
Referring to FIG. 1, the conventional nitride-based semiconductor light-emitting device includes a n-type nitride semiconductor layer 12, an active layer 13 having a multi-quantum well structure, a p-type nitride semiconductor layer 14 which are sequentially formed on a substrate 11. In this case, the p-type nitride semiconductor layer 14 and the active layer 13 are partially sequentially etched so as to externally expose the n-type nitride semiconductor layer 12. Thereafter, an n-type electrode layer 15 is formed on the exposed n-type nitride semiconductor layer 12 and a p-type electrode layer 16 is formed on the p-type nitride semiconductor layer 14.
As described above, after the semiconductor light-emitting device has been completed, wire bonding is performed on each electrode layer. Performing the wire bonding on each LED chip entails a problem in that it requires much time and the manufacturing cost of the LED increases. A flip-chip type light-emitting device has been developed to solve such a problem.
FIG. 2 is a cross-sectional view illustrating a conventional flip-chip type light-emitting device according to the prior art.
As shown in FIG. 2, the flip-chip type light-emitting device includes a n-type nitride semiconductor layer 22, an active layer 23 having a multi-quantum well structure and a p-type nitride semiconductor layer 24 which are sequentially formed on a substrate 21. In this case, the p-type nitride semiconductor layer 24 and the active layer 23 are partially removed so that a part of the top surface of the n-type nitride semiconductor layer 22 is exposed externally. An n-type electrode layer 25 is formed on the top surface of the exposed n-type nitride semiconductor layer 22 and a p-type electrode layer 26 is formed on the p-type nitride semiconductor layer 24.
After the thus formed light-emitting device is turned upside down, the n-type electrode layer 25 and the p-type electrode layer 26 are connected to conductive patterns 29 formed on a submount 27 by means of a bump 28.
In the meantime, the flip-chip type light-emitting device permits a reflective layer to be interposed between the p-type nitride semiconductor layer 24 and the p-type electrode layer 26 to reflect light incident to the p-type electrode layer toward the transparent substrate so as to improve luminance and easily externally emit the heat generated inside the light-emitting device through the electrodes.
However, Ag used as a material for the reflective layer has a problem in that the cohesive force between the Ag and the p-type nitride semiconductor layer 24 is very low, which causes a product defect and makes it difficult to secure a stable contact resistance. Besides, an example of other metals usable as a material for the reflective layer includes Al, Ni, Ti, Pt and the like. But these metals encounter a problem in that they have a relatively low reflection efficiency as compared to Ag.